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# Forum: Biostatistics

Epidemiology and biostatistics, public health research. GLM, logistic regression, survival analysis, clinical trials.

1. ### Dunnett's test for longitudinal data

Dear Stats Folk, I have a one Control group and one patient group. I have measurements on Controls at one time point, while I have a single...

• Replies: 0
• Views: 2,481
04-30-2013, 05:22 PM
2. ### Help needed for the interpretation of ANOSIM results in Primer

As new to biostatistics I would appreciate some help on the interpretation of ANOSIM results in Primer. Thank you!!...

• Replies: 0
• Views: 4,324
04-29-2013, 09:02 AM
3. ### Time*predictor interaction term for longitudinal study analysis

Hello Forum, Currently I am analyzing results of longitudinal study evaluating the effects of possible dichotomous predictor on continious outcome...

• Replies: 0
• Views: 3,680
04-28-2013, 10:07 PM
4. ### Compare the variations of bacterial species between test groups

Hello, I have been scratchiong my head for a few days on this problem, which should be pretty simple. I really hope someone can point me in the...

• Replies: 0
• Views: 2,295
04-28-2013, 10:46 AM
5. ### Odds ratios less than 1, how to make interpretation ?

Hello all, How do I make interpretation of odds ratio equal to 0.02, given from a logistic model with a binary outcome and let's say 2 treatments...

• Replies: 5
• Views: 36,784
04-28-2013, 12:33 AM
6. ### Wide CI for odds ratio

Hello all, I ran a model that yields odds ratio, like the logistic regression does. I have received a very wide CI. To illustrate the reason,...

• Replies: 5
• Views: 4,068
04-27-2013, 11:50 PM
7. ### More than 2 outcome (categorical), what is the statistical test?

Hello everyone! If I have an outcome (dependent variable) is 3 outcomes (Scale of measurement: categorical/nominal) and the interdependent...

• Replies: 4
• Views: 2,996
04-26-2013, 12:32 PM
8. ### Kaplan-Meier and log-rank analysis

Question about Kaplan-Meier analysis and log rank. I am currently working on a project using the National Cancer Institute's SEER database. A lot of...

• Replies: 0
• Views: 2,653
04-24-2013, 06:03 PM
9. ### A T test question

This is a question on presenting the result of the effectiveness of weight loss program. There is only one group of subject and two time point ( pre...

• Replies: 4
• Views: 1,844
04-23-2013, 04:45 PM
10. ### Design Issue: Retrospective Cohort or Case Control?

Good Morning! I am currently trying to decide which approach to my research question is best. I am using a large data set from a state agency. The...

• Replies: 5
• Views: 3,083
04-22-2013, 09:18 PM
11. ### Testing the assumption of linearity in a multi-level logistic regression analysis

Hello all! I am working on a multi-level logistic regression (Binary Outcome) model and am trying to finding the best way to check the assumption of...

• Replies: 4
• Views: 7,182
04-22-2013, 01:24 PM
12. ### too high CV

Hello friends, when i am analysing my data using ANOVA, i came up with a very large cv(55) is there any means to lower it? my design is 4x5 CRD with...

• Replies: 3
• Views: 2,855
04-20-2013, 08:37 AM
13. ### Test if non-negative measurements are significantly different from 0 (5 replicates)

I have measurements basically indicating how much a gene is used in specific individuals. The way you do this is by counting how much gene product...

• Replies: 1
• Views: 2,792
04-19-2013, 06:12 PM
14. ### Non-inferiority Cox model

Hello, I am trying to design a study in which the primary endpoint is time to event. Due to some constraints, the study needs to be a...

• Replies: 0
• Views: 1,738
04-17-2013, 06:33 AM
15. ### Variable prediction

Hi everyone, I'm currently doing work with morphometry, working with data I've collected and with an already existing database. At the moment I'm...

• Replies: 1
• Views: 1,256
04-17-2013, 05:21 AM
16. ### How to Report Dunnett MCT?

Hello, How do I properly report an ANOVA followed by Dunnett's MCT in APA format? Below is the report minitab generates for Effects of Dose on...

• Replies: 0
• Views: 2,662
04-16-2013, 09:59 AM
17. ### frequency of heterozygous allele between two groups

I am sorry I am not statistician but I have a very simple (maybe stupid:)) question. I have case group of 4460 and controls of 5085, P value is...

• Replies: 0
• Views: 1,231
04-12-2013, 04:47 AM
18. ### control of type I error?

Hello forum, I am seeking your advise. Here is the problem: In a clinical trial, we will collect MRI imaging data from each patient...

• Replies: 3
• Views: 886
04-11-2013, 02:24 PM
19. ### Correct statistical test to compare pre and post questions (dummy variable)

Hi friends, What is the correct statistical test to compare a group who was tested in two points in time (pre and post) The same people. I have...

• Replies: 2
• Views: 2,153
04-11-2013, 08:55 AM
20. ### Comparing Qualitative Integer Scores: Non-parametric alternative to ANOVA needed?

I am trying to analyze data from the longitudinal qualitative scoring of knee joints to measure differences in disease severity by a number of...

• Replies: 0
• Views: 1,323
04-10-2013, 10:09 AM
21. ### Mann-Whitney U and Bonferroni Correction

I recently presented some work in my department in which my colleagues and I had applied a Mann-Whitney U test for multiple pairwise comparisons. We...

• Replies: 3
• Views: 12,580
04-08-2013, 09:31 AM
22. ### Removing interaction effect on 2-way ANOVA?

Hello, I've run a 2 way ANOVA of my research results and got these 3 p-values: A=0.001, B=0.069, and A*B=0.167. My professor now wants me to remove...

• Replies: 1
• Views: 4,764
04-07-2013, 09:02 PM
23. ### multivariate Cox regression, ordinal variable as dummy variables, and p value

I'm trying to understand a paper on kidney cancer research. The study uses a multivariate Cox regression. The outcome variable is death/no death from...

• Replies: 0
• Views: 2,794
04-05-2013, 02:27 PM
24. ### How do I show something is an 'independent variable'?

Please help. I am totally confused about how to show that something is an independent risk factor. I.e. in a cohort study: Group A (n=1000) -...

• Replies: 2
• Views: 1,827
04-03-2013, 01:04 AM

Hello, I am trying to test whether my choice of link function is correct using the goodness-of-link test. So, firstly since I am testing the...

• Replies: 0
• Views: 2,505
04-02-2013, 10:31 PM
26. ### probably any easy question for the stat inclined (not me)

Hi all, A population of patients were tested for 3 viruses and have a variety of symptom questions associated. For example: ...

• Replies: 1
• Views: 1,309
04-02-2013, 07:10 AM
27. ### Sampling Size determination

Hello All I have a population of 22000 individuals. I wanted to mesure a mean value of a specific parameter. for this purpose I randomly tested...

• Replies: 0
• Views: 1,188
03-31-2013, 02:05 AM
28. ### Working out risk factors for a medical complication?

Hi All - HELP! I have a large dataset on women in labour, and I'm interested in finding out risk factors for a particular complication of labour....

• Replies: 2
• Views: 1,535
03-29-2013, 08:19 AM
29. ### How to present data after Holm-Bonferroni Correction

Hi all, I am manually using Holm-Bonferroni method to correct my data as I can't find a way to do it using software. As the data is relatively...

• Replies: 1
• Views: 5,013
03-28-2013, 08:20 PM
30. ### Testing significance of frequencies by position of nucleotide pairs

Hi all, I have a set of frequencies for each of the 16 possible nucleotide pairs at a given position in a sequence. I want to test whether any of...

• Replies: 0
• Views: 2,644
03-28-2013, 06:53 PM
31. ### Sample size with G power

Hello I ran some sample size calculations using Gpower, in order to find the minimum required sample size for the Fisher exact test, since I need...

• Replies: 2
• Views: 4,612
03-27-2013, 09:37 PM
32. ### one way ANOVA for rank data?

I was recently reading up on nonparametric alternatives to one way ANOVA and came across a description of ANOVA on rank data...

• Replies: 0
• Views: 3,851
03-27-2013, 03:02 PM
33. ### Comparing 2 different pop sizes

Hi, I am running up against some problems in my stats analysis. Please can anyone give me a hand on this... I have data on Emergency Department...

• Replies: 0
• Views: 1,486
03-27-2013, 06:54 AM
34. ### Hypothesis testing for very large sample sizes

Hello everyone, I am trying to figure out which hypothesis test is best for my research. I have two groups of patients (Group 1, n = 726,314...

• Replies: 1
• Views: 1,170
03-26-2013, 03:30 PM
35. ### reescaling ?

Hello to all. I'm analizyng a data composed by several paired observations. The first observation is non treated that is the baseline of signal....

• Replies: 0
• Views: 1,398
03-26-2013, 02:05 PM
36. ### Comparing groups-carbohydrate microarray

I have a large dataset representing levels of binding of fluorescently-labelled bacteria to multiple carbohydrates on a microarray, comprised of 88...

• Replies: 1
• Views: 1,212
03-25-2013, 06:00 AM
37. ### Comparing ratios between groups using population estimates with confidence intervals

Based on two national population surveys, I have estimates of rates of event A and event B (with 95% confidence intervals) by age category and...

• Replies: 2
• Views: 1,620
03-20-2013, 01:44 PM
38. ### How do analyze the error bars of a Standard Error statistical test?

Hi I'd be really appreciative if anyone might be able to help me. I'm studying biology at a foundation level and have recently been introduced to...

• Replies: 2
• Views: 5,845
03-19-2013, 08:51 PM
39. ### Using G*power to calculate a priori sample size

My experimental design is very simple: test cells at 0, 50, and 100 uM concentrations of drug and count for toxicity. Using G*power, I'm pretty...

• Replies: 0
• Views: 3,966
03-19-2013, 11:21 AM
40. ### Predicted probabilities for discrete-time event history analysis

Does anyone know how to calculate predicted probabilities for a discrete-time event history analysis? Just in case the term "predicted...

• Replies: 0
• Views: 1,617
03-18-2013, 11:51 AM
41. ### Relationship between sample mean and sample survival probability

I am not sure if this question is very naive, but I was wondering if there is a relationship between sample mean and sample survival probability. For...

• Replies: 2
• Views: 1,363
03-17-2013, 10:11 PM
42. ### Simulation of remission and after remission times under specific conditions

This is basically a data generation problem. Say, t is an exponential lifetime with mean two years. tr is the remission time and ts is the after...

• Replies: 1
• Views: 1,300
BGM
03-17-2013, 10:58 AM
43. ### Sample size for rare events

Hello I need to calculate the sample size for a study with the primary objective being to test the efficacy of a new treatment. The failure rate...

• Replies: 2
• Views: 5,456
03-16-2013, 10:43 AM
44. ### Covariate imbalance and restricted randomization

Dear all, I'm involved in a cluster-randomized clinical trial with 20 clusters and 2 treatment arms, intervention and control. We would like to...

• Replies: 0
• Views: 1,010
03-16-2013, 10:27 AM
45. ### Two therapies in two separate populations over time

Good Evening, I would appreciate any input on the following problem, I have searched around the web to see if I can find a more effective...

• Replies: 2
• Views: 1,847
03-16-2013, 09:36 AM
46. ### calculating % difference

Hi all, I need your help in solving this problem, my data looks like this I.D Var1 1 AA 2 AA 3 AA 4 AA 5 AG 6 ...

• Replies: 4
• Views: 1,491
03-16-2013, 12:17 AM
47. ### Compare independent gene lists after statistical test (limma)

Dear all, I have a general question about the statistical analysis approach that I intend to use, which basically boils down to "is this feasible to...

• Replies: 0
• Views: 1,273
03-14-2013, 10:20 AM
48. ### How do cell biologists perform power of analysis?

Often times you only see POA for clinical studies or studies involving humans. However, I'm under the impression that ANY scientist should perform...

• Replies: 0
• Views: 1,121
03-12-2013, 09:10 PM
49. ### Denominator in rate

Hi! This isn't so much a statistical question as it is just figuring out the appropriate dates in which to include cases into a denominator for a...

• Replies: 0
• Views: 3,480
03-10-2013, 06:54 PM
50. ### p value of 0.000 on SPSS

I am using SPSS to define relationship between two variables. Previous research has indicated a significant relationship between them. Spearman...

• Replies: 6
• Views: 58,812
03-10-2013, 03:16 PM
51. ### Which statistical method will be best for these variables?

I am using three variables in my paper. One is barthel index which is scored out of 100. It measures funtional disability of patients.The lower the...

• Replies: 0
• Views: 2,914
03-10-2013, 09:23 AM
52. ### Relative Risk in logistic regression

Hi all, I am very grateful to all those who write to me 1) how i can obtain relative risk (risk ratio) in logistic regression in R. 2) how to...

• Replies: 3
• Views: 2,653
03-07-2013, 01:17 AM

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